[Charting] format the Linear Axis

I really recommend that you ask questions on Stack Overflow. The chart controls are a huge topic and they should work more or less the same as the Silverlight Toolkit ones since I ported them from there. I might not be able to answer all questions very
quickly here and SO is a place where it might be easier to find help. Just tag your question with winrt, winrt-xaml, silverlight-toolkit, xaml, etc.